Don't Oversimplify Glacier Retreating (and Advancing) Reports

With all the recent brouhaha over inaccurate and since retracted statements in the 2007 IPCC climate change report about the speed with which Himalayan glaciers are melting, a recent series of posts over at China Dialogue is particularly poignant. In it Professor Kenneth Hewitt, research associate at the Cold Regions Research Center of Ontario's Wilfred Laurier University reminds us that the changes happening to Asia's glaciers are more complicated than is commonly presented: Regional Climate Change Variation Means Some Glaciers Advancing as Most RetreatFirst, Prof Hewitt points out that in addition to threats from receding glaciers, there are threats from advancing glaciers. The former are well publicized--changes in water availability being the primary one--but the latter less so. And in the Karakorum Himalaya local conditions ("regionally distinct responses to climate change" in Hewitt's words) are bucking the global trend and causing an advance and thickening of glaciers.

While the headwaters of several of South and East Asia's great rivers are threatened, those of the Indus and Yarkand Rivers are less so.

Winters Bringing More Rain and Less SnowProf. Hewitt says,

None of this is to suggest that climate change is not a serious issue in the Karakoram. In every valley of the region farmers tell me the winters have grown shorter in the past couple of decades, there is less snow and more rain. They report an increase in windstorms and rain during summer. Formerly, clear, sunny weather in autumn was reliable and perfect for drying grain, fruit and winter fodder, and for post-harvest chores around the villages. Not any more. They report increasing problems with damp and mildew from insufficient drying days. Rain and wind threaten the harvest and damage buildings. These are, in fact, more immediate hazards for the mountain communities than anything that may be happening to the glaciers.

Precipitation Changes Greater Issue Than Simple Glacier RetreatThe article goes on to caution about extrapolating the effect of melting glaciers too broadly. You often read claims about billions of people's lives being at risk because of glacial retreat. While this is true at the broadest level because they do live in river basins with retreating glaciers at their head, Hewitt says such a generalization is misleading.

Yes, such are the numbers of people living in river basins withtributaries coming from glacierized mountains. However, in most cases the glaciers are a tiny part of the river flows, notably in the most heavily populated areas of China, India and the south-east Asian mainland. Snowfall affects much vaster areas than the glacier cover, and is more critical. For the vast majority of these populations, rainfall and ground waters are far more important than snowfall. Glacier change can have impacts on these other parts of the hydrological cycle or may compound changes in them, but the processes are mostly indirect and too poorly known to make such generalizations.

The original goes into much greater detail about the specific climate changes and local conditions causing Karakorum glaciers to thicken while most others regionally are retreating, as well as what sort of regional responses are needed. It's well worth a read: Understanding Glacier Changes [PDF]